In bureaucracies and in computer software there’s often debate about what format to use for dates. The essential issue is that in the U.S, we use MM-DD-YY, and in Europe they use DD-MM-YY, and this is a confusing mess.
The answer is incredibly simple and beyond all dispute:
With this format, there is no misunderstanding anywhere ever. With a four digit year first, only months can come next and everyone knows this. And only days can come after that.
It will also never suffer from turn-of-the-century problems. You’ll never have ridiculous panic like we had with Y2K.
An incredibly useful side-effect of this date format is that an alphanumeric sort of a collection of dates happens to exactly match a chronological sort. This remains true if it is followed by a time (in HH:MM:SS format, of course).
Slashes versus dashes is not a major issue, except that slashes conflict with Unix/Linux/Mac file path names, so if you want to use a date in a filename, you’re either going to use dashes or lose them entirely (YYYYMMDD).
This is the One True Date Format. Always use it. Use it in databases, on web forms, on paper forms, in filenames, in log files. Print it on T-shirts and shout if from the rooftops. Put it on billboards and in sky-writing. Use it in transmissions to outer space when we contact aliens. Tattoo it on your forehead (please don’t, that idea was a joke). Make fun of anyone using other heretical date formats, and be merciless about it (this part is serious again).
Join with me in this, and together we will rule the world.